The present invention relates to a process of producing a container from glass, in particular of a container the shape of a hollow body open on both ends, more particularly in the shape of a syringe barrel, which is in particular suited for pharmaceutical and medical applications.
Pharmaceutical containers normally are made from tubes or by blow forming directly from the melt. Due to lower variations in thickness, containers made from tubes can be made with thinner wall thicknesses and with close wall thickness tolerances. As a result of the wall thickness problem, containers in the form of syringe barrels for pharmaceutical or medical applications are produced exclusively from tubes.
GB 572 984 proposes to form a syringe with an at least closely toleranced wall thickness by blowing using a blowpipe, and snap back forming on a mandrel, but this is a process where more than 50% of the glass is lost and has to be discarded, so that this process hardly lends itself to industrialization.
DE 1 241 057 A further discloses a production process for ampoules for pharmaceutical and medical purposes directly from the melt, where the glass quantity required is initially drawn from the glass melt using a blowpipe and is then blown, with the blowpipe rotating, into a two-part mold that is applied from the outside. According to another method of producing ampoules directly from the glass bath, the bottom of the melt pan comprises an opening through which the liquid glass is pressed out by a plunger from the top toward the bottom. The glass drop is cut off by automatically operated shears and drops into a funnel-like recess where it is retained either by vacuum or by a ring placed on top of the drop. A hollow mandrel, which is introduced automatically, then blows up the parison to form a hollow body.
These and other variants of a production process for ampoules do not guarantee satisfactory thickness tolerances for production of syringe barrels.
Accordingly, a production process based on preformed glass tubes has become generally accepted in the art for the production of pharmaceutical containers in the form of syringe barrels.
The drawbacks of that method are relatively high production cost and the fact that local reheating of the glass tube during the reforming process will result in depletion of certain components due to evaporation. For example, containers made from glass tubes normally will be depleted of boron and sodium in different surface areas when the containers are produced from borosilicate glasses. In addition, intermediate packaging and transportation to the reforming station of the tubes used as a starting material require additional measures if undesirable contamination or damage to the tubes is to be prevented.
As a rule, so-called “Type I glasses”, sometimes also described as “neutral glasses”, are used for the production of pharmaceutical or medical containers of the kind of interest in the present case. The glasses in question, as a rule borosilicate glasses, have a Class I resistance to water according to DIN ISO 719 and a Class I resistance to acids according to DIN 12116.